Users interact with computing devices for a wide variety of purposes, both professional and personal. For example, radiologists frequently interact with and control medical image diagnostic work stations in order to view patient images. In this and other settings, users frequently sit in front of their computer display with their forearms and hands resting upon the desk or other work surface upon which the computer display and/or various input devices such as a keyboard, a mouse and/or a touch sensitive surface are placed. In this pose, a user is prepared to provide input via the keyboard, via the mouse or via a touch sensitive surface that may also be supported by the desk or other support surface.
A computer mouse is useful for the control of a cursor or the like upon a graphical user interface and, as such, is useful for tracking and pointing applications. However, a computer mouse does not generally permit user input in the form of expressive gestures. Instead, in addition to the user input provided via movement of the computer mouse, user input provided via a computer mouse is generally provided by the user's actuation of the left and right mouse buttons and/or the user's actuation of a scroll wheel. In addition to the constraints upon the form of user input provided via a computer mouse, frequent interaction with a computer mouse may cause discomfort or fatigue as a result of the tight grasp that some users maintain upon the computer mouse in order to move the mouse, click the mouse buttons and/or roll the scroll wheel.
In order to allow for more expressive gestures, multi-touch and stylus-capable touch tablets and track pads have been introduced. Although the touch tablets and track pads are configured to receive and interpret a wider array of gestures as acceptable forms of user input, some users may interact with touch tablets and track pads by raising their hand from the underlying support surface, such as the desk, upon which the touch tablet or track pad rests such that only one or more of their fingertips contact the touch sensitive surface of the touch table or track pad. Over an extended period of use, a user may become fatigued or otherwise experience discomfort associated with having to maintain their hand in a raised position while providing the touch input. Other users may interact with touch tablet and track pads by sliding the heel of their hand along the desk or other surface upon which the touch tablet or track pad rests while permitting one or more of their fingertips to touch the touch sensitive surface of the touch tablet or track pad, thereby limiting their range of input and potentially creating at least some discomfort.